Motor relay

ABSTRACT

In preferred form a starting relay for an electric motor having a wire wound electromagnetic coil and a pivotal armature attached thereto. A normally open contact pair comprising one fixed contact and one movable contact on said armature are closed upon pivotal movement of said armature in response to electromagnetic force of the coil during motor start. A cantilevered leaf spring on said armature is contracted at its free end by a calibrating screw on the coil. Adjustment of the calibrating screw with respect to the leaf spring sets a predetermined spring bias in opposition to the electromagnetic force holding the armature against the coil and therefore the relay may be set to open the starting contacts at a predetermined current level in the coil.

United States Patent 2,915,683 12/1959 Lewus 3,256,402 6/1966 Linkous ABSTRACT: In preferred form a starting relay for an electric motor having a wire wound electromagnetic coil and a pivotal armature attached thereto. A normally open contact pair comprising one fixed contact and one movable contact on said armature are closed upon pivotal movement of said armature in response to electromagnetic force of the coil during motor start. A cantilevered leaf spring on said armature is contracted at its free end by a calibrating screw on the coil. Adjustment of the calibrating screw with respect to the leaf spring sets a predetermined spring bias in opposition to the electromagnetic force holding the armature against the coil and therefore the relay may be set to open the starting contacts at a predetermined current level in the coil.

MOTOR RELAY This invention relates to starting relays for split phase electric motors.

It is known in the relay art to utilize an electromagnetic coil to pivot an armature and close a pair of start contacts connected to the phase winding of an electric motor. Normally the coil is connected to the supply conductors in series with the main winding of the electric motor. When the motor is started the relatively large current flow through the motors main winding and the coil causes the armature to pivot toward the coil and engage contacts connected to the phase winding.

The magnetic force produced by the coil is proportional to the current flowing through the coil and its effect on the armature is inversely proportional to the square of the distance between the armature and the coil. In prior relays the spacing between the coil and the armature is determined by a stop arm which is bent to calibrate the relay. Changing the distance between the armature and the coil in this manner causes the starting contacts to open and close at a predetermined current level. The labor cost to perform this bending adjustment is significant.

The present relay includes an electromagnetic coil and an armature which is pivotal with respect to the coil. A contact movable with the armature engages a fixed contact as the armature is pivoted toward the coil. To vary the force necessary to pivot the armature toward the coil and engage the starting contacts a calibrating screw on the coil bears against a leaf spring on the armature. Adjustment of the calibrating screw varies the preload force on the calibrating spring and changes the response of the armature to current through the coil.

The procedure for calibrating the present relay requires the imposition of only two currents to the coil. Prior relays adjusted by bending the stop member require three or four current levels, one for pickup (contacts closed), one for pull in (armature all the way over), one for dropout (contacts open), and one for nonpickup. By applying a predetermined pickup current to the coil of the present relay, with the calibrating screw out from the leaf spring, the contacts can be observed in engagement. By subsequently applying a lower dropout current and adjusting the calibrating screw, the contacts disengage.

Therefore an object of the inventor in the present invention is to provide a starting relay for electric motors having an armature pivotal with respect to an electromagnetic coil and having a resiliently mounted leaf spring on the armature coactive respectively with a fixed contact and a calibrating screw to vary the armatures response to electromagnetic force of the coil.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIG. 1 is a planar view of the relay with the start contacts in a normally open position; and

FIG. 2 is a fragmentary planar view of the relay with the start contacts closed.

In FIG. 1 of the drawings a relay is illustrated. Relay 10 includes a flat base portion 12 of insulating material such as phenolic. An elongated bar core 14 is attached to base 12 and an electromagnetic coil 16 is formed on its upper end by multiple wraps of insulating wire. A lead 18 of the coil 16 is electrically connected to bar core 14. The core 14 is electrically connected at its upper end by a stop member 20 which is connected to terminal 22. Terminal 22 is connected by a conductor 24 to supply conductor L through a current overload protector 26 and a control switch 28. The other lead 30 of coil 16 is electrically connected to a terminal 32 on the base 12. Terminal 32 is connected by conductor 34 to supply conductor L through the main winding 36 of an electric motor 38.

A pivotal steel armature 40 is connected to the lower end of core 14 by a thin beryllium spring hinge 42. Spring hinge 42 is secured between a backing plate 44 and the end of core 14 by welding. The spring hinge 432 is secured to armature 40 by projection welds 46. The hinge 42 and backup plate 44 permit limited pivotal movement of hinge 40 with respect to core M and coil 16. The stop member 20 limits clockwise rotation of the armature 40 with respect to coil 16 as shown in FIG. ll. Beryllium is a desirable material to utilize for spring hinge 412 because of its desirable fatigue resistance.

An offset member 48 is attached to the armature 40 by rivets 50 and mounts an arm 52 having contact 54 at its end. The arm 52 is secured to the offset member 48 by welding. Another contact 56 is affixed to a terminal 58 on base 12 and is adapted to engage contact 56 when the armature 40 moves counterclockwise in FIG. 1 toward the coil 16 in response to electromagnetic force of coil 16. Terminal 58 is connected by conductor 60 to the supply conductor L through a capacitor 62 and the phase winding 64 of motor 38.

Armature 40 is rotated counterclockwise from the normal run position shown in FIG. 1 to the start position shown in FIG. 2 in response to electromagnetic force on the armature caused by the flow of current through coil 16. Lead weights 66 on the free end of armature 40 increase the armatures moment of inertial to prevent chattering of the contact pair caused by the character of AC current in the coil. Felt pads 68 on weights 66 cushion the armature as it moves between the position shown in FIG. 1 and FIG. 2.

When control switch 28 is closed, current flows from supply conductor L, through the overload protector 26, conductor 24, terminal 22, stop member 20, core 14, lead 18, coil 16, lead 30, terminal 32, conductor 34 and the main winding 36 to the supply conductor L The current through coil 16 produces an electromagnetic force which attracts armature 40 toward the coil and into the start position shown in FIG. 2. The term pickup describes the operation of the relay which engages contacts 54 and 56. counterclockwise movement of armature 40 closes contacts 54 and 56 and completes a circuit from supply conductor L through control switch 28, overload protector 26, conductor 24, terminal 22, stop member 20, core 14, spring 42, armature 40, offset member 48, arm 52, contacts 54 and 56, terminal 58, conductor 60, capacitor 62 and the phase winding 64 to supply conductor L The flow of current through phase winding 64 aids in bringing motor 38 up to speed. As the speed of motor 38 increases, the current through coil 16 drops until the electromagnetic force produced by the coil is insufficient to hold the armature 40 in the position shown in FIG. 2. The term dropout describes the operation of the relay which disengages contacts 54 and 56. When the armature 40 returns to its normal run position shown in FIG. 1, contacts 54 and 56 are disconnected and the circuit through the phase winding 64 is open.

In a typical Frigidaire refrigerator such as Model FPCD-200VP which has a A-horsepower split phase motor, the relay is set to pick up (close the start contacts) at a maximum current of 10.5 amperes. The relay must be calibrated to drop out (open the start contacts) at a minimum current of 9.5 amperatures.

The relay 10 includes a calibrating device for armature 40 to vary the force needed to engage contacts 54 and 56. This calibrating device includes a cantilevered leaf spring 70 which is attached at one end to the armature 40 by rivets 50. The free end of spring 70 is ofiset from the armature 60. A calibrating screw 72 is threadably supported by a central portion 73 of core 14. The rounded end 74 of screw 72 contacts the leaf spring 70 to bias the armature and therefore vary force necessary to pivot armature 40 toward coil 16.

The procedure for calibrating the relay to the proper pickup and dropout limits is as follows. The calibrating screw is backed away from the leaf spring and a predetermined pickup current is applied to the relay coil. The contacts should then close. Next a reduced dropout current is applied to the relay coil. Then the calibrating screw is advanced toward the spring until the start contacts open to reset the relay for subsequent starting operation. Rechecking the relay at pickup and dropout currents then is performed.

While the embodiments of the present invention as hereindescribed constitutes a preferred form, it is to be understood that other forms may be adapted.

I claim:

1. A start control for an electric motor having main and phase windings and supply conductors comprising:

an electromagnetic relay including an elongated conductive core attached to an insulating base;

insulated wire wrapped around one end of said core to form an electromagnetic coil;

a conductive armature pivotal with respect to said core;

one end of said armature and one end of said core connected by a flat conductive metal spring hinge which allows pivotal movement of said armature with respect to said core;

a contact arm on said armature;

a contact on the free end of said contact arm movable with said armature;

a fixed contact on said base located to engage said movable contact when said armature pivots toward said coil;

a cantilevered leaf spring supported at one end by said armature and with its free end offset from said armature;

a calibrating screw threadably supported by said core and adapted to contact the free end of said leaf spring;

a first lead of said electromagnetic coil electrically connected to a first supply conductor;

a second lead of said electromagnetic coil electrically connected to a second supply conductor through the main winding of the electric motor; and

said movable contact and said fixed contact completing a circuit from said first supply conductor through the motors phase winding to said second supply conductor and whereby rotation of said calibrating screw varies the force on said leaf spring to change the resistance of armature to pivot toward said coil.

2. A start control for an electric motor having main and phase windings and supply conductors comprising:

an electromagnetic relay including an elongated conductive core member attached to an insulating base;

insulated wire wrapped around one end of said core to form an electromagnetic coil;

a conductive armature member pivotal with respect to said core;

one end of said armature and one end of said core connected by a conductive flat metal spring hinge which allows pivotal movement of said armature with respect to said core;

a contact arm on said armature;

a contact on the free end of said contact arm movable with said armature;

a fixed contact on said base located to engage said movable contact when said armature pivots toward said coil;

a cantilevered leaf spring supported at one end by one of said members and with its free end offset from the said one member;

a calibrating screw threadably supported by the other of said members and adapted to contact the free end of said leaf spring;

a first lead of said electromagnetic coil electrically connected to a first supply conductor;

a second lead of said electromagnetic coil electrically connected to a second supply conductor through the main winding of the electric motor; and

said movable contact and said fixed contact completing a circuit from said first supply conductor through the motors phase winding to said second supply conductor and whereby rotation of said calibrating screw varies the force on said leaf spring to change the resistance of said armature to pivot toward said coil.

3. The relay as set forth in claim 1, wherein said first lead of said electromagnetic coil is electrically connected to said conductive core; and said core is electrically connected to said first supply conductor and whereby said core is a conductor for current to said coil and to said movable contact.

4. The relay as set forth in claim 2, wherein said first lead of said electromagnetic coil is electrically connected to said conductive core; and said core is electrically connected to said first supply conductor and whereby said core is a conductor for current to said coil and to said movable contact. 

1. A start control for an electric motor having main and phase windings and supply conductors comprising: an electromagnetic relay including an elongated conductive core attached to an insulating base; insulated wire wrapped around one end of said core to form an electromagnetic coil; a conductive armature pivotal with respect to said core; one end of said armature and one end of said core connected by a flat conductive metal spring hinge which allows pivotal movement of said armature with respect to said core; a contact arm on said armature; a contact on the free end of said contact arm movable with said armature; a fixed contact on said base located to engage said movable contact when said armature pivots toward said coil; a cantilevered leaf spring supported at one end by said armature and with its free end offset from said armature; a calibrating screw threadably supported by said core and adapted to contact the free end of said leaf spring; a first lead of said electromagnetic coil electrically connected to a first supply conductor; a second lead of said electromagnetic coil electrically connected to a second supply conductor through the main winding of the electric motor; and said movable contact and said fixed contact completing a circuit from said first supply conductor through the motor''s phase winding to said second supply conductor and whereby rotation of said calibrating screw varies the force on said leaf spring to change the resistance of armature to pivot toward said coil.
 2. A start control for an electric motor having main and phase windings and supply conductors comprising: an electromagnetic relay including an elongated conductive core member attached to an insulating base; insulated wire wrapped around one end of said core to form an electromagnetic coil; a conductive armature member pivotal with respect to said core; one end of said armature and one end of said core connected by a conductive flat metal spring hinge which allows pivotal movement of said armature with respect to said core; a contact arm on said armature; a contact on the free end of said contact arm movable with said armature; a fixed contact on said base located to engage said movable contact when said armature pivots toward said coil; a cantilevered leaf spring supported at one end by one of said members and with its free end offset from the said one member; a calibrating screw threadably supported by the other of said members and adapted to contact the free end of said leaf spring; a first lead of said electromagnetic coil electrically connected to a first supply conductor; a second lead of said electromagnetic coil electrically connected to a second supply conductor through the main winding of the electric motor; and said movable contact and said fixed contact completing a circuit from said first supply conductor through the motor''s phase winding to said second supply conductor and whereby rotation of said calibrating screw varies the force on said leaf spring to change the resistance of said armature to pivot toward said coil.
 3. The relay as set forth in claim 1, wherein said first lead of said electromagnetic coil is electrically connected to said conductive core; and said core is electrically connected to said first supply conductor and whereby said core is a conductor for current to said coil and to said movable contact.
 4. The relay as set forth in claim 2, wherein said first lead of said electromagnetic coil is electrically connected to said conductive core; and said core is electrically connected to said first supply conductor and whereby said core is a conductor for current to said coil and to said movable contact. 